Portable terminals, such as mobile phones, or PDAs (Personal Digital Assistants), can be driven by a rechargeable battery. If a portable terminal uses a rechargeable battery, to charge the battery, a separate battery charger can supply electric power to the portable terminals. The battery charger and the battery can have connection ports formed on the outer surface thereof so that the connection ports come into contact with each other in order to thereby electrically connect the battery charger and the battery.
If the battery charger and the battery have connection ports formed on the outer surface, the connection ports are exposed to the outside and are susceptible to contamination by foreign substances. Contamination by foreign substances can bring about a malfunction in the battery charging. In addition, if the connection ports are exposed to moisture, the charging may not be carried out properly.
Wireless charging technology can use wireless power transmission and reception in which, for example, when the mobile phone is placed on a charging pad, the battery is automatically charged without connecting the battery to a separate charging connector. The wireless charging technology may improve a waterproofing function because the electronic devices are wirelessly charged, and may enhance the portability of the electronic devices by eliminating the wired charger.
The wireless charging technology may be divided into an electromagnetic induction type using coils, a resonance type using resonance, and an RF/Microwave radiation type that converts electric energy into microwaves to then be transmitted.
Moving a magnet with respect to a coil can generate an induction current. If an induction current is generated in a primary coil, the primary coil can generate an electromagnetic field causing an induced current in a secondary coil. The primary coil can be used in a transmitting end and the secondary coil can be used in a receiving end. An induced current can be generated in the receiving end according to a change in the magnetic field.